Re: Doepfer A-100 Modular

From Mark Kolmar
Sent Sat, Apr 22nd 1995, 01:41

On Fri, 21 Apr 1995, Marc Mcnulty (MUSIC) wrote:

> On Fri, 21 Apr 1995, Mark Kolmar wrote:
> 
> One problem with the PAIA kits is that the modules are based on Curtis 
> chips which are no longer manufactured.  This could be a problem in the 
> future if a module fails or you wish to expand. 

I will definitely want to expand.  Other than the possibility that Paia
just has a big box full of these out-of-production chips, why the
built-in, immediate obsolescence?  This is not encouraging.

> > (For example, I used a very modest modular at the U of Ill.  We weren't
> > really supposed to do stuff like this, but I plugged a bass guitar into 
> > at least one of the CV inputs.  It worked great.  Was I just lucky or can 
> > you do that kind of thing without worry and expect it to work?)
> Of course it will work, because the pickups of the Bass make a small 
> voltage, which is read by the CV input as a control voltage.  You can use
> mics, tape, etc. (but only use line level input, no amping) 

That I knew already or I wouldn't have done it ;-) What I'm concerned
about is that small voltage being too much to handle or too little to
work. 

Another issue has to do with different voltage standards.  One example... 
I'll guess a VCA typically behaves this way:  0V CV in = infinite
resistance, (x)V CV in = unity gain, (y)dB attenuation per (z) reduction
in voltage.  If the values of x,y, and z are different from one mfr to
another, then you'd need appropriate EGs as well.  I shudder to think what
you're going to say about CV vs. pitch from one VCO to the next.

> > A good volume of mail on this list seems to be people asking "how to I
> > drive my XXX with my YYY..."  Although these questions mostly seem to do 
> > with sequencing.  I'll need good MIDI to CV (incl. velocity and hopefully 
> > controllers).
> You will need an analog sequencer or the PAIA cv/Midi converter works 
> very well.

That's just the thing:  I didn't see a MIDI/CV in the Paia catalog except 
built into the FatMan.  The FatMan would be a good start if:

a) I can re-engineer it to be freely patchable.  With enough 
documentation this should be very do-able.

b) VCOs did more than just ramp.

c) Other (filter) envelope were also ADSR

d) HP/LP/BP VCF, not just LP.

e) Probably something else I'm forgetting.

> > - Potential hazards while experimenting with feedback loops
> Feedback loops can generate voltages beyond +5/-5v (the loops need to be
> controlled (buffered).

By this, do you just mean you need something either to max-out (e.g. 
distortion pedal=clipping amp) or to otherwise attenuate the signal (e.g.
mixer=resistor)?  To me this is a given, but good advice nonetheless.